from collections import defaultdict

from django.db.models import Sum, Count, Case, When, Q, Value
from django.db.models.functions import Coalesce

from apps.warehouse.models import InventoryQuotaSaleTransaction, InventoryQuotaSaleItem


class TransactionDashboardService:

    @staticmethod
    def get_dashboard(org):
        transactions = InventoryQuotaSaleTransaction.objects.filter(
            seller_organization=org
        )

        transaction_stats = transactions.aggregate(
            total_transactions=Count("id"),
            success_transactions=Count("id", filter=Q(transaction_status="success")),
            failed_transactions=Count("id", filter=Q(transaction_status="failed")),
            waiting_transactions=Count("id", filter=Q(transaction_status="waiting")),
            total_amount=Coalesce(Sum("price_paid"), 0),
            total_weight=Coalesce(Sum("weight"), 0),
            unique_ranchers=Count("rancher", distinct=True),
        )

        items = InventoryQuotaSaleItem.objects.filter(
            transaction__seller_organization=org
        ).select_related("gov_product", "free_product")

        products_stats = items.values(
            product_id=Case(
                When(gov_product__isnull=False, then="gov_product_id"),
                When(free_product__isnull=False, then="free_product_id"),
            ),
            product_name=Case(
                When(gov_product__isnull=False, then="gov_product__name"),
                When(free_product__isnull=False, then="free_product__product__name"),
            ),
            product_type=Case(
                When(gov_product__isnull=False, then=Value("gov")),
                When(free_product__isnull=False, then=Value("free")),
            )
        ).annotate(
            total_sales=Count("id"),
            total_weight=Coalesce(Sum("weight"), 0),
            # total_price=Coalesce(Sum("total_price"), 0),
            # avg_unit_price=Coalesce(Sum("total_price") / Sum("weight"), 0),
            success_sales=Count("id", filter=Q(transaction__transaction_status="success")),
            failed_sales=Count("id", filter=Q(transaction__transaction_status="failed")),
            waiting_sales=Count("id", filter=Q(transaction__transaction_status="waiting")),
            card_payments=Count("id", filter=Q(transaction__price_type="card")),
            cash_payments=Count("id", filter=Q(transaction__price_type="cash")),
            check_payments=Count("id", filter=Q(transaction__price_type="check")),
            credit_payments=Count("id", filter=Q(transaction__price_type="credit")),
            extra_items=Count("id", filter=Q(is_extra=True)),
            pre_sale_items=Count("id", filter=Q(is_pre_sale=True)),
        ).order_by("-total_sales")

        # calculate sum of item share percentage by product
        items_by_product = defaultdict(list)

        for item in items:
            pid = item.gov_product_id or item.free_product_id
            items_by_product[pid].append(item)

        for product in products_stats:
            pid = product["product_id"]
            share_totals = defaultdict(lambda: {"total_price": 0, "count": 0})

            for item in items_by_product.get(pid, []):
                if item.item_share:
                    for share in item.item_share:
                        # share: {"name": ..., "price": ..., "shaba": ...}
                        name = share.get("name")
                        price = share.get("price", 0)

                        share_totals[name]["total_price"] += price
                        share_totals[name]["count"] += 1

            product["item_share_stats"] = sorted(
                [
                    {"name": name, **val}
                    for name, val in share_totals.items()
                ],
                key=lambda x: -x["total_price"]
            )

        return {
            "transaction_summary": transaction_stats,
            "product_summary": list(products_stats),
        }